The long-term objectives of this proposal are to improve and standardize the management of Acute Lower Intestinal Bleeding (ALIB), and to achieve formal training in health services research for the applicant. The proposed research plan and didactic curriculum utilize the many resources available in the Harvard Medical Community to foster Dr. Strate's demonstrated interest in outcomes research and will ensure her career as an independent investigator. The studies outlined in this proposal will evaluate outcomes and care practices in ALIB. ALIB is a frequent, costly and under-studied disorder. Multiple strategies exist for the diagnosis and treatment of ALIB, and studies comparing these strategies are limited. Our previous work defined risk factors for severity in ALIB with the intent of identifying patients appropriate for aggressive interventions. This work also reinforced reports suggesting that colonoscopy, particularly when prompt, is an effective intervention. However, significant uncertainty remains regarding its efficacy, feasibility and safety, and radiographic interventions are frequently utilized. The degree of variation in care practices, reasons for this variation and its effect on patient outcomes are not known. Therefore, the specific aims of this proposal are to compare the impact of colonoscopy versus radiographic interventions for ALIB on rebleeding, morality and resource utilization, and to assess physicians' practices and factors that influence clinical decision making. Three complementary studies will address these aims. 1) A statewide database will be used to study 7,000 patients with ALIB. Data will be abstracted on hospital and patient characteristics, clinical findings on admission, procedural interventions, and resource utilization. Propensity score methods will be employed to statistically estimate the causal effects of each intervention. 2) A prospective cohort of 300 patients admitted to three hospitals with ALIB will be followed and detailed data collected on procedural interventions and patient outcomes. Follow-up will be obtained 30 days and one year after discharge. Multivariable modeling and propensity scores will be used to adjust for confounding in the analysis. 3) A nationwide survey will be administered to a random sample of 2,000 practicing gastroenterologists. Physicians' practices, barriers to care and beliefs regarding available interventions will be assessed and compared. Understanding the role of available interventions, barriers to care and physicians' attitudes will lead to a more evidence-based approach to the management of ALIB. These studies will also provide the skills and data that are critical for planning future investigations.